Tall oil pitch is a sub-product or residue of tall oil distillation used to obtain fatty acids and rosin acids. Tall oil is obtained from black liquor soaps. These soaps are a sub-product of the Kraft pulping process for conifer trees. Conifer wood, especially pine wood, contains free rosin acids, fatty acids, mostly as triglycerides, a series of non-saponifiable compounds and volatile terpenes. During the pulping process, said compounds are separated from wood. Glycerides of fatty acids and rosin acids are saponified by the alkaline heated liquid and the resulting soaps are dissolved in the pulping liquor. After the digestion the pulping liquor is concentrated and sodium soaps of these mixed acids accumulate at the surface together with neutral compounds. The complex mixture denominated black liquor soaps or tall oil soaps can be separated from the surface. This material, which comprises between 50 and 70% of solids, can be used as fuel or acidified, which yields crude tall oil (CTO). In turn, CTO can be used as fuel or as a source of a series of chemicals.
Black liquor soaps constitute a complex mixture formed by sodium salts of fatty acids, rosin acids, which form the saponifiable fraction of the mixture, and a series of other compounds such as sterols, fatty alcohols or polycosanols, mono- and diterpenes, which together form the non-saponifiable or neutral fraction of black liquor soaps. Treating these soaps with diluted sulfuric acid converts the sodium salts into free fatty acids and rosin acids. Consequently, an aqueous phase containing sodium sulfate and an oil phase containing the remaining components are formed. The oil phase separated from the aqueous phase is denominated “tall oil”.
Tall oil is used to obtain industrial fatty acids known as TOFA (tall oil fatty acids) in the technical literature and rosin acids known as TORA (tall oil rosin acids), which have broad commercial applications. TORA and TOFA are obtained from fractioned distillation under vacuum of tall oil. The distillation bottom or “pitch”, which contain most of the non-saponifiable compounds, have been used as fuel or for preparing asphaltic emulsions.
However, pitch value has increased recently due to a novel process to recover pitch sterols that has been commercially implemented (Arboris LLC). This process has been disclosed in the U.S. Pat. No. 6,297,353. One of the sub-products of the process, denominated light neutral matter, contains significant amounts of tetracosanol. Tetracosanol is by itself a product useful in detergent formulations, but most importantly it can be a convenient raw material for the production of tetracosanoic acid or lignoceric acid, which is an excellent moisturizing agent for shampoos, and cosmetic creams and lotions.
Consequently, the object of the present invention is the development of a process for recovery of tetracosanol from light neutral matter.
Composition of Light Neutral Matter
Light neutral matter is a complex mixture of chemicals with different characteristics, among which about forty chemical compounds have been identified, such as sterols, diterpenoids, monoterpene alcohols, diterpenic aldehydes, long chain aliphatic alcohols, steroid alcohols, hydrocarbons and stilbene-derived compounds. Table 1 shows the components of light neutral matter, a typical average composition and the variation range of its components. Said variability is due to the variability of the raw material used for cellulose production as well as to variations in process conditions, but it has been observed that tetracosanol is not always present among the main components.
TABLE 1Components, typical average composition and composition range of light neutral matter.AveragecompositionCompositionComponent(%)range (%)13-Epimanool0.190.01-15  8(17),E-13-epimanoyl-15-ol0.540.01-15  Abietadiene0.780.01-15  Abietal3.280.1-15 Abietol0.980.1-15 Agatadiol6.290.1-55 Beta sitostanol0.33 0-20Beta sitosterol2.14 0-20Campestanol0.01 0-20Campesterol0.06 0-20Dehydroabietadiene0.390.01-15  Dehydroabietal1.780.1-15 Dehydroabietol0.570.01-15  Docosanol2.580.1-50 Eicosanol0.250.1-30 Stigmasterol0.01 0-20Geranylgeraniol1.800.1-15 Heneicosanol1.060.01-30  Hexacosanol4.320.1-51 Isoagatadiol8.650.1-55 Isopimaradiene1.900.1-15 Isopimaral7.140.1-50 Isopimarol7.030.1-50 Manool0.380.01-15  Neoabietadiene0.200.01-15  Neoabietal0.600.01-15  Neoabietol0.200.01-15  Octacosanol1.260.1-40 Palustral0.200.01-15  Pentacosanol1.080.01-30  Pimaradiene1.400.1-15 Pimaral6.080.1-50 Pimarol6.320.1-30 Sandaracopimaral0.390.01-15  Sandaracopimaradiene0.200.01-15  Sandaracopimarol0.600.01-15  Squalene0.410.01-15  Terpineol0.600.01-15  Tetracosanol10.580.1-60 trans-Comunal0.600.01-15  trans-Comunol6.960.1-45 trans-Pinosylvin dimethyl ester9.210.1-50 Tricosanol0.650.1-20 
Notwithstanding the complex nature of light neutral matter, a surprisingly simple process has been found for the recovery of tetracosanol from light neutral matter, comprising the steps of:                a) forming a mixture by contacting light neutral matter with hexane and heating said mixture to form a solution of light neutral matter in hexane;        b) cooling down said solution to 10° C. or less to form a solid phase and a liquid phase;        c) separating the solid phase from the liquid phase; and        d) fractionating the solid phase through distillation to obtain a fraction comprising tetracosanol.        